1. Field of the Invention
The invention relates to image forming apparatuses such as a copying machine and a printer. More particularly, it relates to an image forming apparatus comprising a unit withdrawably mounted in an apparatus main body.
2. Description of the Related Art
There exists a known image forming apparatus in which a fixing unit including members for performing fixing of a toner image to a recording sheet and is withdrawably mounted in an apparatus main body. In such apparatus, a locking mechanism is provided so as to restrict a movement of the fixing unit at the time when such movement is not needed. However, in a conventional technology, an operation lever for unlocking the locking mechanism provided in the fixing unit had been such a large part extending in a longitudinal direction of the fixing unit that space-saving in the image forming apparatus was prevented.
In view of the above, a various kinds of locking mechanisms which are compact and easy in operation for locking the fixing unit have been proposed. For example, in a construction disclosed in Japanese Unexamined Patent Publication No. HEI8-44131, a movable body which is connected rotatably to a main body of an image forming apparatus by a hinge is provided, and a predetermined locking engaging member is provided in the movable body on which the fixing device is mounted and in the main body of the image forming apparatus. Further, in Japanese Unexamined Patent Publication No. 2003-241615, a fixing device including a cover member serving as a handle gripped at the time of moving the fixing device and as an operating portion of the locking mechanism is disclosed.
However, in the construction disclosed in the Japanese Unexamined Patent Publication No. HEI8-44131, strength of the exterior cover is likely to be lowered since a part of the exterior cover is cut off and an operation lever for the locking mechanism is provided therein. Consequently, it would be necessary to add strength separately, or the part itself becomes larger and may prevent downsizing of the apparatus.
Further, in a construction disclosed in the Japanese Unexamined Patent Publication No. 2003-241615, a fixing cover is separately provided at an inner part of the exterior cover of the apparatus. Therefore, a user may be required to withdraw the fixing device by gripping the fixing cover after opening the exterior cover. It increases a number of operations needed for withdrawing the fixing device. Further, in the case of an image forming apparatus provided with a sheet conveyance passage between the fixing unit and the exterior cover, the operating lever of the locking mechanism prevents a conveyance of a recording sheet. Furthermore, there was a problem that a space between the exterior cover and the fixing unit for treating operation of sheet jamming becomes narrow.